This invention relates to a protection circuit for a current source, and particularly to a protection circuit that allows the compliance voltage of a current source to be greater than a positive power supply or more negative than a negative power supply without damaging the current source.
In circuits that have an excitation current source for providing a current to some other device, the current source has an output voltage compliance, which is the voltage limit that the current source can provide. If the compliance is exceeded, the excitation current source circuitry can be damaged. A manufacturer of a device with such a current source may specify that a user not connect to the current source a device that produces a voltage outside of the compliance range.